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Ice-age flowers Russian scientists have grown flowering plants using seeds stored by squirrels 30,000 years ago and preserved by the Siberian permafrost, a new study shows.

The seeds of the herbaceous Silene stenophylla are by far the oldest plant tissue to have been brought back to life, according to lead researchers Svetlana Yashina and David Gilichinsky of the Russian Academy of Sciences.

The latest findings could be a landmark in research of ancient biological material and the bid to potentially revive other species, including some that are extinct.

The scientists highlight the importance of permafrost itself in the "search of an ancient genetic pool, that of pre-existing life, which hypothetically has long since vanished from the Earth's surface".

The previous record for viable regeneration of ancient flora was with 2000-year-old date palm seeds at the Masada fortress near the Dead Sea in Israel.

The latest success is older by a significant order of magnitude, with researchers saying radiocarbon dating has confirmed the tissue to be 31,800 years old, give or take 300 years.

"For the first time, we managed to recreate a plant with the help of fruits that are 32,000 years old," says Yashina.

Buried during the Pleistocene

The study, which appears this week in the Proceedings of the National Academy of Sciences, described the discovery of 70 squirrel hibernation burrows along the bank of the lower Kolyma river, in Russia's northeast Siberia, and bearing hundreds of thousands of seed samples from various plants.

All burrows were found at depths of 20-40 metres from the present day surface and located in layers containing bones of large mammals such as mammoth, woolly rhinoceros, bison, horse, deer, and other representatives of fauna from the Late Pleistocene Age.

The permafrost essentially acted as a giant freezer, and the squirrelled-away seeds and fruit resided in this closed world - undisturbed and unthawed, at an average of -7°C - for tens of thousands of years.

Scientists were able to grow new specimens from such old plant material in large part because the burrows were quickly covered with ice, and then remained "continuously frozen and never thawed," in effect preventing any permafrost degradation.

"The experiment was successful thanks to the discovery of viable particles from the placenta of three fruits found intact by our colleagues in a squirrel burrow," sats Yashina.

"Preserved in eternal ice in a perfect state, the three fruits had not germinated and has therefore kept the placental tissue cells viable," she adds.

In their lab near Moscow, the scientists originally sought to grow plants from mature S. stenophylla seeds, but when that failed, they turned to the plant's placental tissue, the fruit structure to which seeds attach, to successfully grow regenerated whole plants in pots under controlled light and temperature.

'Legitimate claim'

"This is an amazing breakthrough," says Grant Zazula of the Yukon Paleontology Programme at Whitehorse in Yukon Territory, Canada.

"I have no doubt in my mind that this is a legitimate claim."

Scientists have known for years that certain plant cells can last for millennia under the right conditions.

Some earlier claims of regeneration have not held up to scientific scrutiny, but the Yashina/Gilichinsky team was careful to use radiocarbon dating to ensure that the seeds and fruit found in the permafrost were not modern contaminants from S. stenophylla, which still grows on the Siberian tundra.

Arctic lupines, wild perennial plants in North America, were grown from seeds in a lemming burrow believed to be 10,000 years old and found in the mid-20th century by a gold miner in the Yukon.

Zazula recently used radiocarbon methodology to determine that those seeds were modern contaminants, according to the Times.